Process for the production of formic acid



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Ito Drawing.

lvly invention relates to the production of formic acid by thecombination of carbon monoxide and water in. the presence. of acatalytic agent. The'reaction is essentially a hydrolysis of carbonmonoxide by water, being reversible, and occurring in molecularproportions in accordance with the :tollow ing equation G6 HQQHCUOH inwhich PzPressure ofCU in atmospheres fizfioncentration oi HCOOH in'molsper 1000 g. H O.

f zFugacity of water in the formic acid solution.

f zFugacity of pure KZA constant perature.

The following table shows the results of such a calculation.

water.

' Pressure of. C0 in atmospheres Gone. 01 HCOOH by weight reaction'isordinarily at high temperatures The rate of this 'quite slow exceptwhich are impracticable for use on account of the extremely highpressures which must .be jointly employed, Y

' The objectof my invention is to provide 5% parts.

FEUCESS 180R THE ERODUGTIQN 0F FOEMEIC ACID.

Application filed June 20,1925. Serial lilo. 38,569.

a workable process for the production of .i'ormic :acid by thehydrolysis of carbon monoxide. l have discovered that when carbonmonoxide gas and water vapor, in approximately equi-molecularproportions, are passed under pressure over a cuprous' halide catal stor into a solution or suspension of sue a catalysafthe production oi?formic acid maybe easily efiected.

'lhe requisite mixture of carbon monoxide and water vapor for thereaction may be obtained in several. ways. For example, carbon monoxidemay be generated by various methods known to chemical industry and mixedwith suitable quantities of water vapor before the reaction to formicacid is effected.

l have discovered that cuprous chloride, which is the cuprous halidewhich i prefer to employ, when dissolyed or suspended in solutions ofstrong acid such as sulfuric, hydrochloric, or phosphoric, is a suitablecatalyst for the production of formic acid by the reaction of carbonmonoxide and water. Cuprous chloride reacts with carbon monoxide in thepresence of water to form a double compound which it isbelieved has.theformula-CuGl-CO2H 0. It is be-V I 4 acid, water, and cuprouschloride, thus depending upon the rem e The following formula areindicative of suitable catalyst mixtures:

CuGl, 10 parts; sulfuric acid, 90

parts.- I .4,

- CuCl, 10 parts; 10% sulfuric acid, 90

parts. I

GuCl, 10 parts;

90 arts,

parts; 'lllzqfihosnhoric acid, 90

The, reaction may be carriedout by passing carbon monoxide and watervapor underpressure through a "liqu1d containing the catalyst in theform of a suspension or solution, or the cuprous chloride may bedepositedupon a suitable carrier such as, pumice or some othervoluminous inert material, which may be moistened with the aqueoussolution of thea'cid to be used with 35% hydrochloric acid, v r 95dilthe cuprous chloride, and packed in a tube or vessel of suitableshape through which the gas may be passed so as to make contact with thecatalyst.

When a mixture of carbon monoxide is passed over such a catalytic massunder such conditions of temperature and pressure that the formic ac dcatalyt-ically formed is again volatilized, the reaction issubstantially a continuous one and the continued passage of the gasesover the catalyst causes the continuous formation and volatilization offormic acid. The formic acid may of course be liquefied by cooling thecatalyzed gas mixture. The liquid formic acid may be continuouslyremoved and the gases recirculated, thus making the process a continuouscyclic one. y

The rate of formation of formic acid depends on the temperature,pressure, and the speed of the passage of the gaseous mixture over orthrough the catalyst. The temperature for the hydrolysis of the carbonmonoxide in the presence of the catalyst may be quite low and in generalI prefer to use temperatures of the range 150 C. At such temperatureranges high working pressures are not necessary and in general I preferto use pressures of twenty atmospheres and upward.

It should be observed that the maintenance of exact pressure andtemperature conditions is not essential for the practice of mycatalyticprocess and a wide variance of these conditions is possible in obtainingsatisfactory results.

Now, having fully described my invention, I claim the following as newand novel: 1. A process for the production of formic acid whichcomprises reacting carbon monoxide and water under pressure in thepresence of a cuprous halide catalyst.

2. A process for the production of formic acid which comprises reactingcarbon monoxlde and water under pressure 1n the presence of a catalystcontaining cuprous chloride..

3. process for the production of formic acid which comprises reactingcarbon monoxide and water, at a pressure exceeding. 20 atmospheres, inthe presence of a cuprous halide catalyst.

4.. A process for the production of formic acid which comprises reactingcarbon monoxide and water, at atemperature of between 50-150 C. and at apressure exceeding twenty atmospheres, in the presence of a cuprouschloride catalyst. I

5. A process for the production of formic acid which comprises reactingcarbon monoxide and water, at a temperature of be tween 50-150 C. and ata pressure exceedingtwenty atmospheres, in the presence of a mixture ofcuprous chloride and a mineral acid.

' 6. A continuous process for the produc tion' of formic acid whichcomprises passing a mixture of carbon monoxide and water vapor, underpressure, over a cuproushalide-mineral acid catalyst maintained at sucha temperature that the formed formic acid is volatilized, cooling thereacted gas mixture to remove the formic acid, and recirculating thegaseous mixture.

7. A continuous process for the'production of formic acid whichcomprises passing a mixture of carbon monoxide and water vapor over acuprous chloride-mineral acid catalyst at a temperature over 100 (1.,cooling the reacted gas mixture, removing the condensed formic acid, andrecirculating the gaseous mixture.

In testimony whereof I aflix my signature.

WILLIAM (J. ARsEM.

